Metal propeller for aircraft



H. LEITNER.

METAL PROPELLER FOR AIRCRAFT.

APPLICATION FILED APR. 30. 192|.

Patented July 26, 1921.

UNITED STATES HENRY LEITNER, OF KINGSWAY, LONDON, ENGLAND.

METAL PROPELLER FOR AIRCRAFT.

Specification of Letters Patent.

Patented July 26K, 1921.

application inea Apriiso, 1921. semi No. 465,740.

To all whom it may concern Be it known that I, HENRY Lni'riann, a 4subject of'the King of Great Britain, re-

siding at Regent House, Kingsway, London, England, have invented new and useful Improvements in Metal Propellers tor Aircraft, of which the following is a specication.

This invention relates to metal propellers for aircraft, the blades of which are hollow and either rigidly secured to the hub or boss or detachable therefrom and have their faces and backs formed of metal plates secured together at their edges by welding, brazing or the like.

With propeller blades of the described construction it is found that the heating to which the blades are subjected durin the welding or like operation tends to distort them and the invention has forits object to prevent, 'control or correct such harmful distortion.

According to my invention I slit or divide longitudinally either or both of the metal plates constituting the face and back of each blade but preferably the former, the division extending along either the-whole .length or part only of the plate. This construction enables the plates to expand and contract freely during the welding or like process without producing permanent distortion.

The correct shape of the blade having been attained in a suitable welding jig, the' slit'or division'is then covered with a strip of metal which is riveted or otherwise secured to the blade, or the edgesof the metal constituting both sides of the slit may be arranged to overlap and be secured together by riveting or otherwise.

To enable the invention to be fully understood, I' will describe it by reference to the accompanying drawing, in which Figure l is an elevation of a detachable hollow llaminated blade for a metal propeller having its face provided with .a longitudinal slit extending from the tip to a point about midway of its length, the said slit being yclosed by a metal strip.

Fig. 2 is a section of the blade on the line 2 2, Fig. 1, but drawn to a larger scale and Fig. 3 is an enlarged View of part of this section of the face of the blade showing clearly the method of securing the lliiig-in or covering strip to the blade.

Fig.-l is a View similar to Fig. l of a detachable hollow blade having its face provided with a longitudinal slit extending the full length thereof.

Fig. 5 is a section on the line 5;:3, Fig. 4, but drawn to a larger scale, and

Fig. 6 is an enlarged view of part of this section of the face of the blade and the inner lamina, showing clearly the method of securing the filling-in or covering strip to the blade.

Fig. 7 is a section through the butt end of the blade on the line 7 7, Fig. 4, but drawn to a larger scale, and

Fig. 8 is an enlarged View of part oi this section showing. clearly the method of securinv the filling-in or covering strip tothe butt.

igs. 9, l() and 1l are sections illustrating modifications of the mode of closing the slit or division in the propeller blade.

a is the propeller blade formed of metal plates I), c constituting, respectively, the face and back of the blade, 'the said plates being backed or strengthened toward the butt d by internal metal laminae or plates e, g, /z. The said butt, which is of the type in which the laminaeJ b, c, c, f, g, l1J are strengthened by an outer flanged sleeve and an inner ring j, is of circular form in 'cross section so that it can be held in a correspondingly shaped bearing in the propel* ler hub in which it can berturned to vary the pitch of the propeller.

Referringto Figs. 1, 2 and 3, /c indicates' the slit or division in the face according to the invention, which slit extends longitudinally of the blade from the tip thereof to a point adjacent the upper end of the lamina e. By the provision of the said slit 7c it will be seen that when the two halves of the-propeller blade. composed of the plates c and their respective strengthening laminae'c, f and g, L are placed in position in a suitable welding jig, so that they can be welded together along their edges, as indicated at A, Fig. 2, the divided parts of the blade will be free to expand and contract independently.

Z is` the metal strip for filling in and uniting the edges of the slit L, the said strip being secured to the edges of the slit by sea-ming or folding, as indicated clearly in Fig. 3 at m, and to the lamina c by rivets n as indicated in Fig. l. For further security the seams on each side of the strip Z may be compressed at points along their length by a\metal punch as indicated at o Fig. 1, a few only of the punch marks being shown.

The strip Z instead of being connected to the face I) by seaming as just described, may be connected thereto by rivets, as indicated at p Fig. 9. Or, the said strip may cover the slit lc so as to form a riveted butt joint as indicated in Fig. 10.

In the construction indicated in. Figs. 4 to 8, the slit lo extends the entire length of the propeller blade, the laminael e and f being cut away for the reception of the seams m, as indicated clearly in Figs. 6 and 8, and riveted to the face b as indicated at g. In Fig. 8 these rivets also extend through the sleeve z'.

The two parts of the face b, instead of being connected together in the manner hereinbefore described, may be connected by a lap riveted joint as indicated in Fig. 1l.

Although I have described the face of the propeller blade as being provided with the slit it is to be understood that the back thereof may be similarly provided.

It is also to be understood that my invention is applicable to propellers in which the blades are formed integral with or rigidly secured to the hubs or bosses thereof, the slits lc being afterward closed in any suitable manner.

In addition to preventing harmful distortion, the improved construction of propeller blade results ina stiiening thereof so that no struts or distance pieces are required to connect the face and back together and fluttering or vibration of the tip of the blade and metallic ring are practically entirely eliminated.

Claims.

l. A metal propeller of the kind hereinbefore referred to wherein either of the metal plates constituting the face and back of the blades, or both plates, is or are formed with a slit to enable the welding or other heating operation for connecting the edges of such plates together to be effected without harmful distortion of the said plates, substantially as described.

2. A metal propeller as claimed in claim 1, wherein the slit or slits inthe blades is or are closed by a metal strip or strips connected to the slit plates, substantially as described.

3. A metal propeller having internal lamin and constructed as claimed in claim 2, wherein the lamina l are slit or divided to correspond with the slits in the outer plates and are connected by rivets to the latter, substantially as described.

4. A metal propeller as claimed in claim l, wherein the slit or slits is or are closed by an overlap rivet `A l joint, substantially as described.

HENRY LEIINER 

